To effectively promote the driving power for discharge lamps and improve the optical performance of discharge lamps, a push-pull type inverter inputs driving powers with a 180 degree phase difference therebetween to two input electrodes of a discharge lamp. Such an approach has been an important technical means in discharge lamp technologies. There are R.O.C. patent publications of No. 557073 and No. 557074 disclosing related technologies.
To obtain the sufficient brightness of liquid crystal panels and achieve the uniformity of the brightness on liquid crystal panels, the push-pull type inverter is usually used to drive multiple discharge lamps. In such a case, the conformability of the currents/the performance characteristics of the lamps is critical. Increasing the number of lamps will increase the number of driver units and will also increase the size of the circuit board of the driver units. Thus, the complexity and cost of fabricating the circuit board rises. There is a piezoelectric conversion/driver unit appearing in the market, wherein a driver unit is used to drive a conversion unit, a plurality of piezoelectric units and a plurality of loads. There are R.O.C. patent publications of No. 559433, No. 588917 and patent No. I242747 disclosing related technologies.
The driver circuit of the discharge lamp usually has arc discharge because of the imperfect contacts, the ambient temperature and humidity and the damaged parts. Therefore, there are various arc discharge protection devices appearing in the market. Refer to FIG. 1 a diagram schematically showing the architecture of a conventional arc discharge protection circuit. As shown in FIG. 1, a PWM (Pulse Width Modulation) controller 10, a switch 22 and a voltage booster 24 are arranged before each discharge lamp 26 and used to control the driving power transmitted from a power source to the discharge lamp 26. The region between one switch 22 and the input electrode of the corresponding discharge lamp 26 is defined to be a high voltage output section 20. Each high voltage output section 20 has an arc discharge protection device 30 used to detect arc discharge. Once detecting a signal of arc discharge, the arc discharge protection device 30 sends a power-shutting signal to the PWM controller 10 to entirely stop or pause outputting driving power to the discharge lamp 26. There are R.O.C. patent publications of No. 591976 and No. 591839 disclosing related technologies.
However, when the abovementioned arc discharge protection device is applied to the abovementioned push-pull type inverter or the abovementioned multiple-load driving circuit, it cannot perform an appropriate switch-off action when one single lamp of a liquid crystal panel or the transformer thereof is abnormal. For example, when the abovementioned arc discharge protection device is applied to the abovementioned multiple-load driving circuit, and when any one of the loads is abnormal, the arc discharge protection circuit switches off the multiple-load driving circuit; thus, all the lamps of the liquid crystal panel are shut off, and the whole liquid crystal panel fails. When the abovementioned arc discharge protection device is applied to the abovementioned push-pull type inverter, and when the driver circuit at one input electrode side of a single arc lamp is abnormal, the abovementioned arc discharge protection circuit will only stop or pause the operation of the driver circuit at the abovementioned input electrode side, but the driver circuit at the other input electrode side persists in inputting driving power to the discharge lamp; thus, the related electronic devices are likely to be damaged.